Dividing a model by intersecting geometry parts
The new Intersect Tool added in 2.72 will cut up intersecting faces - this is for meshes that are part of the same object, not multiple intersecting objects and can be found in Mesh->Face->Intersect.

Campbell explains it in this video

There are a couple of addons that can help with boolean operations.

One is Blender sculpt tools - the name is a bit misleading as it also works outside of sculpt mode.

Another is BoolTool